Motor and armature manufacturing method

ABSTRACT

An insulator covering the teeth ( 31 ) of an armature ( 3 ) in an inner-rotor motor is composed of a tooth insulator ( 321 ), outer-side insulator ( 322 ), upper-end insulator ( 323 ), and lower-end insulator ( 324 ). The tooth insulator ( 321 ) is composed of substantially annular top and bottom members that are assembled from above and below to the teeth ( 31 ).

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to inner-rotor electric motors and tomethods of manufacturing the armature for inner-rotor motors.

2. Description of the Related Art

The armature in an inner-rotor motor is provided with a plurality ofteeth that, directed inward, protrude from the inner circumferentialsurface of a cylindrical core back, and a conductor is wound onto,electrically isolated from, the teeth to form the coils. Known methodsof forming the coils include a technique in which winding is carried outby inserting the needle of a winding machine into narrow, groove-likeslots between the teeth, and a technique in which a specialized inserteris employed to insert the teeth into conductor wire that has been woundinto a special coil form in advance.

In an inner-rotor motor, however, the slots between the teeth open intothe confined space along the center shaft, and forming the coil is thusnot easy. This makes it difficult to achieve a sufficiently highslot-fill factor. It is also desirable, however, to minimize the gapbetween the teeth in order to reduce the cogging torque of the motor.

As conventional art for solving the foregoing problem is a technology inwhich a core member is constituted from a tooth module unitarily formedby circularly joining the inner circumferential edges of a plurality ofteeth disposed in a radial fashion, and a core back portion that isseparably attached to the outer periphery of the tooth module, and inwhich a conductor is wound onto each of the teeth, which each have beenfitted with an insulating component before the core back portion isattached to the tooth module.

In other conventional art, meanwhile, is a technology in which a statoris manufactured by partially joining with a linker the innercircumferential edges of a radially arranged plurality of teeth andproviding insulating components on each tooth, then winding a conductoraround and attaching a core back portion onto the linked andinsulator-outfitted teeth, and afterwards taking off the linker.

A problem with the foregoing armature is that there are no insulatingcomponents with which the armature can be easily manufactured withoutimpairing the electrical isolation between the conductor and the core(the teeth and core back). In addition, for armatures in theconventional technologies, mention has yet to be made regarding theconfiguration of the insulating components in distributed windingimplementations.

When forming coils by winding the conductor onto the teeth in armaturesof this sort, the coil may protrude above and below from the top andbottom ends of the teeth. In particular, when the coils are formed bydistributed windings, in which the conductor is wound straddling aplurality of teeth, the amount by which the coils protrude isconsiderable, compared with concentrated windings, in which theconductor is wrapped onto each tooth individually. The protruding coilscan be reformed as required, but doing so runs the risk that thereformed coils will come into contact with the top or bottom surfaces ofthe core back, which is not provided with an insulator.

BRIEF SUMMARY OF THE INVENTION

The present invention enables easily and reliably electrically isolatingthe coil from the core in an inner-rotor motor.

A motor of the present invention is an inner-rotor electric motorincluding: a stationary section having an armature; a rotary sectionhaving a field magnet, for generating between itself and the armaturetorque centering on a predetermined center axis; and a bearing mechanismfor rotatably supporting, with the center axis as enter, the rotarysection with respect to the stationary section.

The motor armature has a core that includes a plurality of teethdisposed with the teeth fore edges directed toward the center axis, in aradial pattern with the center axis as center, and a support ring forsupporting the plurality of teeth along their outer side.

The armature also has a tooth insulator covering at least the lateralsides of the plurality of teeth. The armature further includes coilswound around the perimeter of the tooth insulator, around said pluralityof teeth, and outer-side insulators interdigitated with the plural teethand covering the inner circumferential surface of the support ring, theouter-side insulators therein electrically isolating the exterior sideof said coils from the support ring.

The tooth insulator in turn includes a top member attached to theplurality of teeth over their upper end in the orientation parallelingthe center axis, and a bottom member attached to the plurality of teethover their lower end in the orientation paralleling the center axis.

A method of manufacturing an armature of the present invention comprisessteps of: attaching to a plurality of teeth whose fore edges have beentemporarily joined together by a linking member top and bottom membersover the top and bottom of the plurality of teeth axially; and formingcoils by winding conductors onto the plurality of teeth, around theperimeter of the top and bottom members.

In addition, the foregoing method further comprises: a step ofinstalling in an interdigitated fashion between the plural teethouter-side insulators for covering between the teeth the exterior sideof the coils, and attaching to the plurality of teeth a support ring forsupporting the plurality of teeth along their outer side; and a step ofremoving the linking member linking the fore edges of the plural teeth.

From the following detailed description in conjunction with theaccompanying drawings, the foregoing and other objects, features,aspects and advantages of the present invention will become readilyapparent to those skilled in the art.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a vertical section view of a motor;

FIG. 2 is a plan view of a core;

FIG. 3 is an exploded elevational view of a tooth insulator;

FIG. 4 is an underside view of a top member;

FIG. 5 is a fragmentary lateral view of a side member;

FIG. 6 is a partially sectional view fragmentarily depicting the topmember;

FIG. 7 is a partially sectional view fragmentarily depicting a bottommember;

FIG. 8 is a view depicting the top member and bottom member;

FIG. 9 is an elevational view depicting an outer-side insulator;

FIG. 10 is an underside view depicting an upper-end insulator;

FIG. 11 is a flow chart outlining an armature manufacturing method;

FIGS. 12–17 are plan views illustrating an armature;

FIGS. 18 and 19 are elevational views representing the armature; and

FIG. 20 is a plan view depicting the armature.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a vertical section view of an electric motor 1 with an innerrotor according to a preferred embodiment of the invention. Note thatwhen the relative positions and orientations (directions) of the variousparts are described below with reference to top, bottom, right, andleft, these directional references are based on the relative positionsand directions as presented in the accompanying figures, and do notnecessarily denote the relative positions and directions in an actualproduct.

The electric motor 1 is a brushless motor that is used, for example, asthe drive power source for power steering in an automobile. (It shouldbe noted that hatching is omitted from the finely detailed portions ofthe section view.) The electric motor 1 is covered by a cylindricalhousing 11 of which the top end as seen in FIG. 1 is open, and a cover12 that has an opening in the center and covers the opening in thehousing 11. Ball bearings 131, 132 are provided in the opening of thecover 12 and the bottom of the housing 11. The ball bearings 131, 132support the shaft 21 while allowing it to rotate.

A columnar rotor yoke 22 made from a magnetic material is mounted on theshaft 21 inside the housing 11. A multipole field magnet 23 is affixedto the outside surface of the rotor yoke 22. A sintered body containingneodymium, for example, is used for the field magnet 23. On the otherhand, an armature 3 is attached to the inner circumferential surface ofthe housing 11, opposing the field magnet 23.

The armature 3 is disposed with the center axis J1 of the armature 3coaxial with the shaft 21. The armature 3 has a laminated core 30 madeof magnetic silicon steel plates. This core 30 has a plurality of teeth31 extending from the inner circumferential surface of the housing 11 inthe direction toward the shaft 21 and field magnet 23. The plurality ofteeth 31 is furnished with a support ring 33 for supporting the pluralteeth 31 along their outer side.

FIG. 2 is a plan view illustrating the core 30. As shown in FIG. 2, theplural (specifically twelve in this embodiment of the invention) teeth31 are arranged in a radial pattern centered on the center axis J1, withone fore edge of each tooth 31 directed toward the center axis J1. Eachtooth 31 has, in region thereof along the support ring 33 (that is, thedistal portion on the side opposite the center axis J1 side) a firstprotruding portion 311 that bulges in either direction along acircumference centered on center axis J1. This first protruding part 311fits into a recess provided in the inner circumferential surface of thesupport ring 33. Each tooth 31 also has, in the distal portion on centeraxis J1 side, a second protruding part 312 protruding in eitherdirection along a circumference centered on center axis J1. The spacebetween adjacent second protruding parts 312 is a gap 301 (called an“open slot” below) that is vertically (along the center axis J1)elongate.

As shown in FIG. 1 the armature 3 is also furnished with an insulator 32that covers the plural teeth 31. The armature 3 is further furnishedwith coils 35 that are provided by winding the plural teeth 31 with aconductor into multiple layers from the top of the insulator 32. Thecoil 35 is formed by winding the conductor vertically around the outsideof the teeth 31 and insulator 32. Herein, the insulator 32 involvingthis embodiment of the invention is a cast resin article, and iscomposed of a tooth insulator, an outer-side insulator, an upper-endinsulator, and a lower-end insulator as further described below.

A busbar 51 fitted with connectors for supplying drive current to thecoil 35 of the armature 3 is disposed on the cover 12 side of thearmature 3 with respect to the orientation in which the center axis J1extends. This busbar 51 is formed by laminating four arc-shapedconductor plates in the orientation in which the center axis J1 extends,and is packaged in resin so that the terminals protruding from eachconducting plate are exteriorly exposed. An externally leading wire 515,together with the conductor from each coil 35, is connected to eachterminal. A detection circuit board 52 having Hall elements mountedthereon is attached to the cover 12 side of the busbar 51.

The rotor 2 a of this electric motor 1 is composed of primarily rotoryoke 22 and field magnet 23. This electric motor 1 also has a stator 3 acomposed of primarily the armature 3, busbar 51, and detection circuitboard 52 affixed inside the housing 11. The ball bearings 131, 132function as a bearing mechanism supporting the rotor 2 a so that therotor 2 a can rotate relative to the stator 3 a around center axis J1.Supplying drive current through the busbar 51 to the armature 3 producestorque centered on center axis J1 between the armature 3 and fieldmagnet 23, and the rotor 2 a thus turns.

Three Hall elements 53 are mounted on the detection circuit board 52projecting downward together with other electronic parts. These Hallelements 53 are held in a sensor holder. An annular magnet 25 for use asa sensor is attached to the shaft 21 by way of an intervening magneticflange 25 a on the cover 12 side of the field magnet 23. The sensormagnet 25 is opposite the Hall elements 53. Like the field magnet 23,the sensor magnet 25 is a laminated magnet. The position of the fieldmagnet 23 can thus be indirectly detected as a result of the Hallelements 53 detecting the position of sensor magnet 25. Supplying drivecurrent to the armature 3 can thus be controlled based on this detectionresult. The flange 25 a covers the faces of the sensor magnet 25opposite the field magnet 23 and armature 3, and can thus preventinterference with both fields.

FIGS. 3 to 10 illustrate the parts that constitute the insulator 32.FIG. 3 is an exploded elevational view of a tooth insulator 321 thatcovers the surfaces 313 (see FIG. 2) of the plural teeth 31 around whichthe conductor is wound. There are four of these surfaces 313 on eachtooth 31: the two faces perpendicular to the center axis J1, and the twofaces perpendicular to the circumferential orientation centering oncenter axis J1. These surfaces will be referred to hereinafter as “toothlateral sides.” As shown in FIG. 3, the tooth insulator 321 is composedof a top member 3211 which is fit to the plural teeth 31 (see FIG. 1)from one side relative to the orientation in which the center axis J1 isdirected (that is, the upper end), and a bottom member 3212 which issimilarly fit to the plural teeth 31 from the other side (that is, thelower end). The top member 3211 and bottom member 3212 are identicallyshaped. The following description of the top member 3211 shown in FIG. 4and FIG. 5 therefore also applies to the bottom member 3212.

FIG. 4 is a bottom view of the top member 3211 of the tooth insulator321 as seen from the bottom member 3212. As shown in FIG. 4 the topmember 3211 has a plurality of side portions 3213 that cover the sidesof each of the teeth 31 arranged radiating around center axis J1, and aplurality of connecting portions 3214 interconnecting adjacent sideportions 3213 on the center axis J1 side. The side portions 3213 coverthe top surface of the tooth and approximately the upper half of the twoparallel faces descending from opposite sides of the top surface. Asviewed from the center axis J1, the side portions 3213 have anupside-down U-shape as shown in FIG. 6.

FIG. 5 is a side view of one side portion 3213 of the top member 3211.As shown in FIG. 3 to FIG. 5, a interlocking portion 3216 is rendered atthe top end part of each side portion 3213 on the side opposite the sidefacing the center axis J1. Two rim portions 3217 extending vertically,and circumferentially centering on the center axis J1 are provided onthe center-axis J1 side of the interlocking portion 3216.

FIG. 6 and FIG. 7 are partial section views showing part of the topmember 3211 and bottom member 3212. The hatched portions in thesefigures indicate a section through line A—A in FIG. 4. As shown in FIG.6 and FIG. 7, a tapered face 3218 a, 3218 b is rendered to side portions3213 and connecting portions 3214 at the bottom end of the top member3211 and the top end of the bottom member 3212. When the top member 3211and bottom member 3212 are assembled facing each other as they are whenassembled to the core 30, the tapered faces 3218 b of adjacentconnecting portions 3214 face in opposite directions. Though not shownin the figures, the tapered faces 3218 a of adjacent side portions 3213are also formed facing in opposite directions.

FIG. 8 shows the top member 3211 and bottom member 3212 of the toothinsulator 321 assembled to the teeth 31, although the teeth 31 are notshown in the figure. As shown in FIG. 8 when the top member 3211 andbottom member 3212 are attached to the teeth 31, the tapered faces 3218a and 3218 b overlap each other (see FIG. 6 and FIG. 7). A gap is thusprevented from forming between the top member 3211 and bottom member3212. The tooth insulator 321 thus covers the teeth 31 without exposingthe side surfaces 313.

FIG. 9 is a front view of the outer-side insulator 322 disposed betweenthe plural side portions 3213 of the tooth insulator 321. As indicatedby the double-dot dash line in FIG. 4, the outer-side insulator 322 isattach to the outer side of the rim portions 3217 of adjacent sideportions 3213, and is held between the rim portions 3217 and the insidesurface of the support ring 33. Note that for brevity only one of theplural outer-side insulators 322 inserted between all of the sideportions 3213 is shown in FIG. 4.

As shown in FIG. 9 the outer-side insulator 322 has a flange 3221projecting to both sides perpendicularly to the length rendered at onelengthwise end (the top end when the outer-side insulator 322 isinstalled to the tooth insulator 321) of the outer-side insulator 322.When the outer-side insulator 322 is installed, the flange 3221 is heldbetween the interlocking portion 3216 and rim portions 3217 of the toothinsulator 321, and the outer-side insulator 322 is held stationary withboth long sides of the outer-side insulator 322 along the rim portions3217. The length of the long side of the outer-side insulator 322 (thevertical sides as seen in FIG. 9) is equal to the length of the longside of the tooth insulator 321. As a result, the opening formed on theopposite side as the center axis J1 of the connecting portions 3214 whenthe top member 3211 and bottom member 3212 are mated is closed by theouter-side insulator 322 (see FIG. 4).

FIG. 10 is a bottom view of the upper-end insulator 323 attached to thetop of the tooth insulator 321. As shown in FIG. 10 this upper-endinsulator 323 is a substantially annular thin plate with steppedrecesses rendered in the bottom inside circumference portion. Aplurality of recesses 3231 are additionally rendered in these steppedrecesses. The end portions of the plural side portions 3213 of the topmember 3211 indicated by the double-dot dash line in FIG. 10, that is,the outside surfaces of the interlocking portion 3216, are fit intothese recesses 3231. Though not shown in the figures, the lower-endinsulator attached to the bottom of the tooth insulator 321 isconstructed identically to the upper-end insulator 323, and has aplurality of recesses into which the flanges 3216 of the bottom member3212 fit. The upper-end insulator 323 covers the top surface of thesupport ring 33, which fits on a specific part on the top of the toothinsulator 321. The lower-end insulator 324 likewise covers the bottomsurface of the support ring 33, which fits on a specific part on thebottom of the tooth insulator 321.

Assembly of all outer-side insulators 322 and the upper-end insulator323 and lower-end insulator 324 to the tooth insulator 321 is describedfurther in the following description of the armature 3 manufacturingprocess.

FIG. 11 is a flow chart of the process for manufacturing an armature 3for an electric motor 1 as described above. FIG. 12 to FIG. 20 show thearmature 3 at different stages in the manufacturing process. FIG. 12 toFIG. 17 and FIG. 20 are plan views, and FIG. 18 and FIG. 19 are frontviews.

As shown in FIG. 12, the first step in manufacturing an armature 3 is toarrange teeth 31 with the second protruding parts 312 on the inside(that is, toward the center axis J1) and the teeth 31 in a ringradiating from the center axis J1, and provisionally connect adjacentsecond protruding parts 312 by means of linking member 34 so that theplural teeth 31 are connected in unison (step S11). The teeth 31 andconnecting members 34 are formed by stamping silicon steel plate toproduce plural pieces. A specific number of these pieces are thenlaminated together. The pieces forming the linking member 34 are stampedfrom silicon steel together with the pieces forming the teeth 31,momentarily separated within the die from the teeth 31, and then onceagain fit together with the teeth 31.

Subsequently, silicon steel is die cut with a die for the support ring33, and the support ring 33 is prepared by putting into form andlaminating a plurality of the individual pieces that make up the supportring 33 (step S12). It will be appreciated that step S11 preparing theteeth 31 and step S12 preparing the support ring 33 could be parallelprocesses, or step S12 could precede step S11. Furthermore, the piecesforming the teeth 31 and linking member 34 and the pieces forming thesupport ring 33 could be stamped from a single sheet of silicon steel atthe same time.

Once the teeth 31 and support ring 33 are prepared, the top member 3211is assembled to the teeth 31 from above as shown in FIG. 13, thuscovering the top half portion of the tooth lateral surfaces 313. Thebottom member 3212 is also assembled to the bottom of the teeth 31, thuscovering the bottom half portion of the tooth lateral surfaces 313. Alllateral surfaces 313 of the plural teeth 31 are thus covered by thetooth insulator 321 (step S13). It will be readily apparent that thebottom member 3212 could be assembled to the teeth 31 first, or the topmember 3211 and bottom member 3212 could be assembled to the teeth 31 atthe same time.

Once the tooth insulator 321 has been attached to the teeth 31, sixconductors are wound onto the plural teeth 31 as shown in FIG. 14 withthe tooth insulator 321 between the conductor and teeth 31, thusresulting in a plurality of coils 35 (six in this embodiment of theinvention) (step S14). The coils 35 are formed as distributed windingsin which the conductor is wound so as to straddle two or more of theplural teeth 31. In the present embodiment the conductor is wound so asto straddle three teeth 31. The coils 35 are thus electrically isolatedby the tooth insulator 321 from all lateral surfaces 313 of the teeth31. Because the coil 35 of this armature 3 is formed by winding theconductor from the outside of the teeth 31 where the gap betweenadjacent teeth 31 is wide, the conductor can be wound as easily as thearmature of an outer rotor motor.

Once the coils 35 are wound, the outer-side insulators 322 are insertedparallel to the center axis J1 on the outside of the rim portions 3217adjacent to the tooth insulator 321 and are thus affixed to the pluralteeth 31 as shown in FIG. 15 covering the outside surface 351 (that is,the side of the coil 35 farthest removed from the center axis J1 betweenthe teeth 31) of the coil 35 between adjacent teeth 31 (step S15). Eachouter-side insulator 322 is held between the first protruding part 311of the two adjacent teeth 31, and the two rim portions 3217 of the toothinsulators 321 rendered to the two teeth 31. As a result, the outer-sideinsulators 322 close the opening formed on the outside (that is, theside farthest from the center axis J1) between two adjacent teeth. Theflanges 3221 formed on both sides of the outer-side insulator 322 (seeFIG. 9) are also disposed between the interlocking portion 3216 and rimportions 3217 of the tooth insulator 321. The bottom of the flange 3221simultaneously contacts the top of the teeth 31. As a result, theouter-side insulator 322 is held firmly in place.

Once the outer-side insulators 322 are in place, the support ring 33 isassembled to the outside of the plural teeth 31 as shown in FIG. 16(step S16). The inside surface of the support ring 33 is covered by theouter-side insulators 322 between the teeth 31. As a result, theouter-side insulator 322 reliably electrically isolates the outsidesurface 351 of the coil 35 and the support ring 33. The plural rimportions 3217 of the tooth insulator 321 also oppose the support ring 33at the opposite end of the teeth 31 as the center axis J1 (that is, atthe support ring 33 side of the teeth 31).

As shown in FIG. 17 and FIG. 18, the upper-end insulator 323 andlower-end insulator 324 are then assembled to the top and bottom sidesof the support ring 33 (see FIG. 18), thus covering the top and bottomsurfaces of the support ring 33 (step S17). As shown in FIG. 17 and FIG.18, the top and bottom end parts of the plural outer-side insulators 322fit into the recesses 3231 in the upper-end insulator 323 and lower-endinsulator 324 (see FIG. 10). This arrangement renders the pluralouter-side insulators 322 between the upper-end insulator 323 above andthe lower-end insulator 324 below, and easily and reliably fixes theouter-side insulators 322 between the tooth insulator 321 and supportring 33. The armature 3 resulting from step S17 has the coils 35protruding greatly above the upper-end insulator 323 and below thelower-end insulator 324 because a large diameter conductor that isdifficult to bend is wound around a plurality of teeth 31.

After the upper-end insulator 323 and lower-end insulator 324 are thusassembled, the top and bottom portions of the coils 35 protruding aboveand below the teeth 31 and support ring 33 (that is, the core 30) arereformed as shown in FIG. 19 and FIG. 20 by pressing the exposedportions of the coil to the outside away from the center axis J1 (seeFIG. 20) and to the top and bottom surface of the core 30 (that is, thetop and bottom of the tooth insulator 321, as well as the upper-endinsulator 323 and lower-end insulator 324) (step S18). This reducesprotrusion of the coils 35 from the core 30. The tops and bottoms of thecoils 35 also move from the top or bottom of the teeth 31 shown in FIG.17 to the support ring 33 side shown in FIG. 20. Reforming the coils 35in this armature 3 renders the coils 35 close to the top and bottomsurfaces of the support ring 33, but the upper-end insulator 323 andlower-end insulator 324 prevent the reformed coils 35 from directlycontacting the top and bottom surfaces of the support ring 33.

The linking member 34 temporarily joining the second protruding parts312 of the plural teeth 31 (denoted by the double-dot dash line in FIG.20) is then removed, thus releasing the provisionally connected pluralteeth 31 and completing manufacture of the armature 3 (step S19). Thelinking member 34 can be easily removed from the armature 3 because thelinking member 34 was first completely separated from the teeth 31 andthen fit back thereto. As shown in FIG. 20, the open slots 301 that arethe gaps between the ends of the plural teeth 31 on the center axis J1side are closed by the connecting portions 3214 of the tooth insulator321. Note that because the teeth 31 are held by the support ring 33, theteeth 31 will not fall out of place when the linking member 34 isremoved.

As described above, the armature 3 of an electric motor 1 according tothe present invention has a plurality of coils 35 formed by winding aconductor around the outside of teeth 31, outer-side insulators 322rendered between the coils 35 and a support ring 33 which is attachedafter the coils 35 are formed, and these outer-side insulators 322prevent direct contact between the outside surfaces 351 of the coils 35and the inside surface of the support ring 33.

Furthermore, a tooth insulator 321, which is composed of substantiallyannular top and bottom members 3211, 3212 assembled to the teeth 31 fromabove and below, covers the lateral surfaces 313 of the teeth 31 andthus prevents contact between the coils 35 and teeth 31. The coils 35and core 30 can thus be easily and reliably electrically isolated in aninner-rotor motor 1. Note that an insulator covering other portions ofthe core 30 can also be provided.

The coils 35 in the armature 3 of the present invention are made with adistributed winding and the coils 35 thus protrude more above and belowthe core 30 than if the coils 35 were made using a concentrated windingwrapping a conductor to each individual tooth 31. The coils 35 are thendeformed greatly to the outside (that is, toward the support ring 33) inthe reforming process. However, contact between the coils 35 and the topand bottom surfaces of the support ring 33 is prevented when the top andbottom portions of the coils 35 protruding from the core 30 are reformedbecause the top and bottom of the support ring 33 are protected byupper-end insulator 323 and lower-end insulator 324 in the armature 3 ofthe present invention, and the coils 35 and the core 30 are thusreliably isolated.

This structure of an armature 3 having the top and bottom surfaces ofthe support ring 33 covered by upper-end insulator 323 and lower-endinsulator 324 is particularly well suited to a motor 1 having coils 35formed with a distributed winding.

The tooth insulator 321 in this armature 3 is separated into a topmember 3211 and a bottom member 3212 which are affixed from oppositesides to the plural teeth 31, thus making it simple to assemble thetooth insulator 321 to the teeth 31. The manufacturing cost is alsoreduced and the manufacturing process simplified as a result of the topmember 3211 and bottom member 3212 having the same shape.

Foreign matter (such as pieces of conductor and varnish) is alsoprevented from passing from the stator 3 a side to the rotor 2 a sidethrough the open slots 301 as a result of the connecting portions 3214of the tooth insulator 321 occluding the open slots 301.

Yet further, the teeth 31 can be easily and completely covered withoutexposing any portion of the teeth 31 because the tapered faces 3218 a,3218 b of the top member 3211 and bottom member 3212 overlap. The edgesof the tapered faces 3218 a, 3218 b are also not exposed to the lateralsurfaces 313 of the teeth and thus will not damage the conductor.

Both side edges of the outer-side insulator 322 are held between thefirst protruding parts 311 of two adjacent teeth 31 and two rim portions3217 of the tooth insulator 321, and the outer-side insulator 322 inthis armature 3 can thus be held by a simple structure. Furthermore, byassembling the outer-side insulator 322 to the teeth 31 before thesupport ring 33 is attached, the outer-side insulator 322 can beinstalled more easily than if the outer-side insulator 322 were insertedbetween the coils 35 and support ring 33 after the support ring 33 isattached. In addition, the upper-end insulator 323 and lower-endinsulator 324 can be easily installed without interference from thecoils 35 because the upper-end insulator 323 and lower-end insulator 324are attached to the teeth 31 after the support ring 33 is in place, andthe top and bottom parts of the coils 35 are then reformed.

The present invention is described above with reference to a preferredembodiment of the invention, but the invention shall not be limited tothe foregoing embodiment and can be varied in many ways.

For example, the coils 35 could be formed with a concentrated windingdepending upon the drive method of the motor 1. This results in lessprotrusion of the coils 35 above and below the core 30 than results froma distributed winding, and may therefore enable eliminating reformingthe top and bottom parts of the coils 35. It may also be possible toeliminate the upper-end insulator 323 and lower-end insulator 324 insuch an arrangement.

The top member 3211 and bottom member 3212 of the tooth insulator 321are also not necessarily identically shaped.

The open slots 301 are preferably occluded in order to prevent foreignmatter from entering to the rotor 2 a. However, depending upon the sizeof the armature 3 and the shape of the teeth 31, an opening could bepresent in the connecting portions 3214 of the tooth insulator 321occluding the open slots 301.

Furthermore, in order simplify holding and securing the outer-sideinsulator 322, the outer-side insulator 322 is preferably installedusing the structure and method described in the foregoing embodiment ofthe invention. However, the outer-side insulator 322 could be held by adifferent structure determined by the configuration of the coils 35 andteeth 31. For example, the outer-side insulator 322 could be installedto the teeth 31 by inserting both side edges of the outer-side insulator322 to grooves formed in the opposing side surfaces 313 of any twoadjacent teeth 31. In this arrangement the top and bottom edge parts ofthe outer-side insulator 322 do not oppose the upper-end insulator 323and lower-end insulator 324 and can be fixed to the teeth 31 by anothermethod as required.

When manufacturing the armature 3 of the present invention the upper-endinsulator 323 and lower-end insulator 324 could be assembled and the topand bottom portions of the coils 35 could be reformed after the supportring 33 is affixed to the plural teeth 31 and the linking member 34 isremoved.

A motor 1 according to the present invention can be used, for example,in electrically-assisted power steering systems, electronic brakesystems, electromagnetic suspension systems, and transmission systems inmotor vehicles, in systems assisting operation and control ofnon-automotive vehicles such as trains, and other applications inindustry, the home, and office automation.

The outer-side insulator in the foregoing embodiment of the invention iscomposed of multiple parts, but the invention shall not be so limited toa specific number. More particularly, two or more outer-side insulators,or a seamless unitary outer-side insulator made by bonding a pluralityof outer-side insulators, could be used.

1. An inner-rotor electric motor comprising: a stationary section havingan armature, the armature furnished with a core formed by laminating aplurality of thin sheets; a rotary section having a field magnet, forgenerating between itself and said armature torque centering on apredetermined center axis; and a bearing mechanism for rotatablysupporting, with the center axis as enter, the rotary section withrespect to the stationary section; said armature comprising: a pluralityof teeth disposed with the teeth fore edges directed toward the centeraxis, in a radial pattern with the center axis as center, a support ringfor supporting said plurality of teeth along their outer side, a toothinsulator covering at least the lateral sides of said plurality ofteeth, said tooth insulator including a top member attached to saidplurality of teeth over their upper end in the orientation parallelingthe center axis, and a bottom member attached to said plurality of teethover their lower end in the orientation paralleling the center axis,wherein said top member and said bottom member interlink along theorientation paralleling the center axis, coils in which conductors arewound over said tooth insulator, around said plurality of teeth, and aplurality of outer-side insulators interdigitated with the plural teethand therein covering the inner circumferential surface of the supportring, said outer-side insulators for electrically isolating the exteriorside of said coils from said support ring.
 2. A motor as set forth inclaim 1, wherein: said armature further comprises annular upper-end andlower-end insulators, covering the top and bottom sides of said supportring; and said coils are formed by distributed winding in which theconductors are wound on straddling two or more teeth among saidplurality of teeth, and then the upper and lower portions of the coilsare reformed.
 3. A motor as set forth in claim 2, wherein the upper andlower end portions of said plurality of outer-side insulatorsrespectively oppose the upper-end and lower-end insulators.
 4. A motoras set forth in claim 1: said tooth insulator having, in a region on thesupport-ring side of said plurality of teeth, a plurality of rimportions opposing said support ring; and said plural teeth each having,in the region on the support-ring side of said plurality of teeth,protrusions bulging along a circumferential orientation centered on thecenter axis; wherein in between the protrusions on any two teethadjoining each other, and the two rim portions of said tooth insulatorwhere provided on said any two teeth, one of said outer-side insulatorsis retained.
 5. A motor as set forth in claim 1, wherein the interspacebetween the fore edges of said plural teeth are closed off by said toothinsulator.
 6. A motor as set forth in claim 1, wherein said plural teethare each attached, in a region on the support-ring side of saidplurality of teeth, to the inner circumferential portion of said supportring.
 7. An inner-rotor motor armature having a core formed bylaminating a plurality of thin sheets, the armature comprising: aplurality of teeth disposed with the teeth fore edges directed towardthe center axis, in a radial pattern with a center axis as center; asupport ring for supporting the plurality of teeth along their outerside; a tooth insulator covering at least the lateral sides of theplurality of teeth, said tooth insulator including a top member attachedto said plurality of teeth over their upper end in the orientationparalleling the center axis, and a bottom member attached to saidplurality of teeth over their lower end in the orientation parallelingthe center axis, wherein said top member and said bottom memberinterlink along the orientation paralleling the center axis; coils inwhich conductors are wound over said tooth insulator, around saidplurality of teeth; and a plurality of outer-side insulatorsinterdigitated with the plural teeth and therein covering the innercircumferential surface of the support ring, said outer-side insulatorsfor electrically isolating the exterior side of said coils from saidsupport ring.
 8. An armature as set forth in claim 7, further comprisingannular upper-end and lower-end insulators, covering the top and bottomsides of said support ring, wherein: said coils are formed bydistributed winding in which the conductors are wound on straddling twoor more teeth among said plurality of teeth, and then the upper andlower portions of the coils are reformed.
 9. An armature as set forth inclaim 8, wherein the upper and lower end portions of said plurality ofouter-side insulators respectively oppose the upper-end and lower-endinsulators.
 10. An armature as set forth in claim 7: said toothinsulator having, in a region on the support-ring side of said pluralityof teeth, a plurality of rim portions opposing said support ring; andsaid plural teeth each having, in the region on the support-ring side ofsaid plurality of teeth, protrusions bulging along a circumferentialorientation centered on the center axis; wherein in between theprotrusions on any two teeth adjoining each other, and the two rimportions of said tooth insulator where provided on said any two teeth,one of said outer-side insulators is retained.
 11. An armature as setforth in claim 7, wherein the interspaces between the fore edges of saidplural teeth are closed off by said tooth insulator.
 12. An armature asset forth in claim 7, wherein said plural teeth are each attached, in aregion on the support-ring side of said plurality of teeth, to the innercircumferential portion of said support ring.